Publication WO-A-03/050456 describes a magnetic refrigeration device with magnetocaloric material which uses two permanent magnets and comprises a one-piece annular enclosure delimiting compartments with magnetocaloric material, for example gadolinium, in porous form, these compartments being separated by joints. Each compartment comprises at least four openings, including an inlet and an outlet connected to a hot circuit on the one hand, and an inlet and an outlet connected to a cold circuit on the other. Both permanent magnets are led into a continuous rotational movement so as to successively sweep the various fixed magnetocaloric material compartments and subject them to variations in magnetic field. The calories and/or frigories emitted by the magnetocaloric material are collected in the hot and cold circuits by heat transfer fluid and sent to heat exchangers. The permanent magnets are driven into rotation by an electric motor that also drives rotary joints so that the heat transfer fluid pipe that runs through the fixed magnetocaloric material compartments is successively connected to the hot and cold circuits. This device, which therefore simulates the operation of a liquid ring, requires accurate, continuous and synchronous rotation of the various rotary joints and permanent magnets.
The movement, especially the linear drive or the rotational drive, of the magnets that generate the magnetic field, the variation of which, due to the linear or rotating movement, causes the temperature cycles of the magnetocaloric materials, requires driving means which usually consist of a traditional electric motor. It will be noted that traditional magnetocaloric materials tend to heat up almost instantaneously as they enter a magnetic field. So-called reverse magnetocaloric materials have the particularity of cooling down as they enter a magnetic field. The generation of calories or that of “negative” calories, so-called frigories, offers various benefits depending on the applications being considered.
The motor that drives the movement of the magnets has a certain size which adds to the overall dimensions of the device, increases its cost, weight and volume and reduces its efficiency, all of which represent disadvantages that impede the development of this technology, particularly when generating cold, despite the solution's undeniable ecological benefit.
U.S. publication 2005/0120720 A1 proposes a magnetocaloric generator in which the electric motorization is integrated and comprises coils wound around the poles of a stator, the rotor being free to rotate and made up of permanent magnets. In this embodiment, the magnetocaloric elements are arranged radially on each side of the poles. They are consequently away from the permanent magnets, are not subjected to the maximum magnetic flux and cannot produce their optimum thermal performances, which impedes the generator's global thermal efficiency. Moreover, the temperature of these magnetocaloric elements rises due to their proximity with the coils which leads to a detrimental effect of thermal remanence.